AlphaMatteShrinkandGrow

The node assumes that an upstream keyer, roto, mask workflow, or source asset already provides a meaningful alpha. If that source matte is fundamentally wrong, morphology can only reshape the error; it cannot infer the intended foreground from color or scene semantics.

Morph Operation provides four distinct behaviors. Shrink contracts the opaque/white region, Grow expands it, Opening is useful for removing small white foreground speckles or protrusions, and Closing is useful for filling small black holes or cracks inside a foreground matte.

Shape defines the geometry of the morphology operator. Circle is a safe organic starting point, Square trends toward rectilinear geometry, and Diamond behaves differently around diagonals and corners. At extreme settings the kernel shape can visibly change the silhouette.

Radius controls the amount of the normal morphology pass. Increase it gradually: large values quickly erase hair, motion blur, semi-transparent edges, and thin geometry even when the broad silhouette appears cleaner.

Output / Process determines what is returned. RGB (Blank Alpha) keeps RGB while blanking alpha; Alpha (RGB Unaffected) modifies alpha while preserving RGB and is the usual matte-engineering mode; RGB + Alpha applies the operation to both parts of the result.

Preview Alpha is a diagnostic view for holes, speckles, edge thickness, and fine detail. It should be used while tuning, then disabled so the final composite can be checked over bright and dark backgrounds.

Manual Iteration Control exposes direct operator application controls. Resolve 21 documents Operator Radius as the size of the operator and Repeat Operation as a repetition control that creates more extreme adjustments. Repeated morphology accumulates damage quickly on fine detail.

Effect Mask is a separate optional coverage input. It does not become the matte that Shrink/Grow processes; the source alpha still lives in the main Input and the blue mask only limits where the processed result contributes.

A practical workflow is to fix the upstream key first, choose the operation that matches the defect, use the smallest useful radius/repetition, inspect Preview Alpha, and then judge the final edge in motion over real backgrounds. Despill and contaminated edge color remain separate tasks.

Conceptually the tool is related to ErodeDilate, but this article describes the dedicated Resolve FX Key interface: four morphology operations, Shape, Radius, Process, Preview Alpha, and conditional manual-iteration controls.